The 150 ms / 300 ms round trip was the "simulated" ping time. They ran real ping tests over 24 hours to the most remote coverage location at the Cook Islands. [wikipedia.org]

One was from Surrey, England to the Cook Islands and averaged 570-800ms round trip -- the other was from California, US to the Cook Islands and averaged 420-620ms round trip. These were performed once per second for 24 hours and can be found in Figure 5 of the research paper. [arxiv.org]

Good question. According to their FAQ [o3bnetworks.com] their satellites will be capable of delivering "gigabytes of capacity". Obviously that would be split among individual beams, and sliced up into smaller pieces for individual service providers and again for individual people. It is based on the Ka-Band which currently supports about 500 megabits per beam (with multiple beams).